The former intelligence analyst's leak of hundreds of thousands of classified documents, mostly about the U.S. wars in Iraq and Afghanistan, has sparked a wide debate about government secrecy and First Amendment rights.
Manning, who was born male and known as Bradley, transitioned to being a woman after the government convicted the former soldier of leaking the documents.
The appeal argues that the sentencing was overreaching, stating, "For what PFC Manning did, the punishment is grossly unfair and unprecedented. No whistleblower in American history has been sentenced this harshly. Throughout trial the prosecution portrayed PFC Manning as a traitor and accused her of placing American lives in danger, but nothing could be further from the truth."
The appeal also argues that Manning released the documents for the good of the public, who had the right to know what was going on.
"PFC Manning disclosed the materials because under the circumstances she thought it was the right thing to do. She believed the public had a right to know about the toll of the wars in Iraq and Afghanistan, the loss of life, and the extent to which the government sought to hide embarrassing information of its wrongdoing," the appeal states.
ABC News previously reported that the judge in the Manning case, Col. Denise Lind, called Manning's conduct "both wanton and reckless" in court documents. Lind added that it "was of a heedless nature that made it actually and imminently dangerous to others."
Nancy Hollander, one of Manning's attorneys, told ABC News today that she "really is a very brave courageous young woman to have done what she did and to write about it. She did what she believed was right in a very difficult situation. What happened with her is really an outrageous sentence, especially when you compare it to others."
Manning, who is currently serving out her prison sentence at the military’s detention facility in Fort Leavenworth, Kansas, wrote about the appeal in her own words on her blog. "I have asked the judges to dismiss all charges or give me a shorter sentence," Manning wrote, outlining alleged errors in her trial. "All in all, rather than this being the end, this is only beginning."
The American Civil Liberties Union, historically a strong defender of First Amendment rights, wrote an amicus brief to the judges of the U.S. Army Court of Criminal Appeals in support of Manning. The ACLU argues that the conviction and sentence of Manning under the Espionage Act must be overturned for two main reasons.
"First, the Espionage Act is unconstitutionally vague, because it provides the government a tool that the First Amendment forbids: a criminal statute that allows the government to subject speakers and messages it dislikes to discriminatory prosecution. Second, even if the Act were not unconstitutional in all its applications, the military judge’s application of the Act to PFC Manning violated the First Amendment because the military judge did not permit PFC Manning to assert any defense that would allow the court to evaluate the value to public discourse of any of the information she disclosed," the amicus brief, posted on the ACLU website reads.
The Electronic Frontier Foundation also posted an amicus brief in defense of Manning, calling for U.S. Army Court of Criminal Appeals to reverse her conviction.